Countergravity casting apparatus

Abstract

Apparatus for the countergravity casting of molten metal by immersing of gas-permeable multi-piece mold in an underlying pot of molten metal includes a motor actuated plunger for pressing the pieces into sealing engagement with each other without the need for glue therebetween and for resisting destructive flexure of the mold incident to the application of casting vacuum thereto.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. Apparatus for the vacuum countergravity casting of molten metal comprising: a mold comprising a porous gas-permeable upper shell at least in part defining a mold cavity and a lower portion adapted for immersion into a pot of said metal underlying said mold, said lower portion including at least one gate in the underside thereof for admitting said metal into said cavity upon evacuation of said cavity;   a vacuum box defining a vacuum chamber confronting said upper shell for evacuating said cavity through said shell, said box including a peripheral edge on the underside thereof defining a mouth receiving and sealingly engaging said lower portion;   means for mounting said mold to said mouth with said lower portion in sealing engagement with said edge;   at least one plunger projecting from said box and recedable into said chamber for permitting mounting of said mold to said mouth and for thereafter pressing of said shell against said lower portion during said evacuation;   a motor for actuating said plunger to effect said pressing; and   means for controlling said motor so as to apply sufficient force on said plunger to sealingly engage said shell and said lower portion and to prevent destructive flexure of said mold during said evacuation but insufficient force to dislodge said mold from said mouth.   
     
     
       2. Apparatus for the vacuum countergravity casting of molten metal comprising: a mold comprising a porous gas-permeable upper shell at least in part defining a mold cavity and a lower portion adapted for immersion into a pot of said metal underlying said mold, said lower portion including at least one gate in the underside thereof for admitting said metal into said cavity upon evacuation of said cavity;   a vacuum box defining a vacuum chamber confronting said upper shell for evacuating said cavity through said shell, said box including a peripheral edge on the underside thereof defining a mouth receiving and sealingly engaging said lower portion;   means for mounting said mold to said mouth with said lower portion in sealing engagement with said edge;   at least one plunger projecting from said box and movable between retracted and extended positions;   a motor for moving said plunger between said positions; and   means for controlling said motor so as to cause said plunger to retract into said chamber for mounting said mold to said box and thereafter to extend and engage said shell with sufficient force to press said shell into sealing engagement with said lower portion and to resist destructive flexure of said mold during said evacuation but insufficient force to dislodge said mold from said mouth.   
     
     
       3. Apparatus for the vacuum countergravity casting of molten metal comprising: a mold comprising a porous gas-permeable upper shell at least in part defining a mold cavity and a lower portion adapted for immersion into a pot of said metal underlying said mold, said lower portion including at least one gate in the underside thereof for admitting said metal into said cavity upon evacuation of said cavity;   a vacuum box defining a vacuum chamber confronting said upper shell for evacuating said cavity through said shell, said box including a peripheral edge on the underside thereof defining a mouth receiving and sealingly engaging said lower portion;   means for mounting said mold to said mouth with said lower portion in sealing engagement with said edge;   at least one plunger projecting from said box and movable between retracted and extended positions;   a fluid motor for moving said plunger between said positions; and   means for controlling the fluid applied to said motor to retract said plunger for mounting said mold to said mouth and thereafter extending and pressurizing said motor sufficiently to press said shell into sealing engagement with said lower portion and to resist destructive flexure of said mold during said evacuation but insufficiently to dislodge said mold from said mouth.   
     
     
       4. Apparatus according to claim 3 wherein said fluid motor comprises a pneumatic cylinder. 
     
     
       5. Apparatus according to claim 3 wherein said control means includes means responsive to the pressure build-up in said motor for triggering cessation of said build-up when said pressure reaches a predetermined cutoff pressure. 
     
     
       6. Apparatus according to claim 3 wherein said control means includes means responsive to the vacuum in said chamber.